If a child expresses difficulty separating from parents, usually mother, on entering school, it is wise to try and understand the cause for this.
Parents often become hooked into merely coping with this behaviour, but thinking about it is usually more useful.
There may be primary emotional difficulties, but often the separation anxiety is secondary to other developmental difficulties the child experiences in the world. If the physical or linguistic world is too challenging, then the child’s security in engaging with that world is mother. Once their developmental difficulties are adequately addressed, they generally grow enormously in confidence.
If the anxiety lies more in the relationship between mother and child, then this is readily addressed with psychological insight and support.